1. Field of the Invention
The invention relates to enhancing voltmeter functionality, and more particularly, enhancing voltmeter functionality for isolating faults in electrical circuitry.
2. Description of the Related Art
Modem vehicles systems incorporate digital (computer) diagnostic systems that can detect many circuit faults in electrical components and systems (e.g., on vehicles). But such systems typically cannot detect all possible circuit faults, for example, high resistance faults caused by corrosion. Moreover, electrical troubleshooting on vehicles and other systems can be time-consuming, labor-intensive, costly, and often ineffective, especially if a component must be disconnected and/or removed for testing circuit continuity.
The vast majority of circuit faults in wiring and connectors result from abuse, exposure, wear, and normal use. Failures in circuit wiring typically are caused by a change in circuit resistance and fall into one of three categoriesxe2x80x94an open circuit, a short-to-ground, or a high resistance (e.g., due to corrosion). Other faults, such as a circuit short to another circuit, can be more obvious because they typically show signs of failure that are easier to discern.
Apparatus typically used to detect electrical faults include ohmmeters, ammeters, and voltmeters. The voltmeter measures voltage (potential difference) at any open in a functional circuit, or voltage drop across a resistance with the circuit intact and operating, which is usually safer and more effective, respectively, than using the ammeter or the ohmmeter. This is because the ammeter must complete a circuit to obtain a reading and the ohmmeter must have all circuit voltage removed and the circuit completely isolated.
A typical voltmeter can, in some circumstances, be used to locate faults, such as those described above. Simply connecting and turning on the voltmeter, however, may be insufficient or inadequate to solve the problem, and require a time consuming effort to reach an incomplete conclusion. For best results the circuit must be active or energized to detect faults, which requires the circuit to be intact and the load to be installed. Further, to prevent corrosive faults from occurring, if the manufacturer intentionally designs wiring and component terminals not to be externally accessible without the component being removed, performing dynamic circuit tests with typical voltmeter leads can be impossible.
Thus, there is a need for effective and relatively inexpensive troubleshooting for detecting electrical circuit faults that is both conclusive and allows for simple dynamic testing.
In one aspect, embodiments of the invention feature circuitry for dynamic testing of a circuit under load. The circuitry includes a test load adapted to be coupled between inputs of a voltmeter, and a switch adapted to short circuit test leads of the voltmeter through the test load.
Embodiments of the invention feature enhanced voltmeter test load circuitry having a test load that can be coupled to or decoupled from the test leads of a voltmeter. The embodiments can be used to help identify the location and type of faults, such as a short-to-ground, an open circuit, and a high (e.g., corrosive) resistance, in a circuit under test. A fuse or circuit breaker can be provided with the enhanced voltmeter test load circuitry for safety reasons. The circuitry can be located within a voltmeter or test leads of a voltmeter, or portions of the circuitry can be located in both. The circuitry can be used systematically in locating and identifying the fault from voltage readings at the location of a removed component or a blown fuse or circuit breaker in the circuit under test. Voltage drop readings are obtained at various points in the circuit under test with the test load both coupled and decoupled between (or effectively coupled between) the test leads. A negative or black test lead can be moved to a convenient machine ground during the test and the test can be repeated to confirm the location of the fault. A change in reading can indicate the fault is on the ground side of the circuit under test while no change can indicate the fault is on the positive side of the circuit under test. Conventional test leads can be used if the load circuitry is incorporated or integrated in the voltmeter or if the load circuitry has a separate coupling or connection to the voltmeter inputs.
Compared to existing methods and devices, embodiments of the invention provide the ability to make a confident and conclusive decision about the type and general location of the electrical fault from component connections, with only two voltmeter readings. No circuit disassembly is required to determine the type of fault, and the user/technician is able to avoid the use of meters less safe than the voltmeter to quantify resistance and current disposition.